/etc/yaws.conf - Configuration file for the yaws webserver

Yaws is fast lightweight webserver. It reads a configuration file called yaws.conf to control its operations. The configuration contains two distinct parts a global part which affects all the virtual hosts and a server part where options for each virtual host is supplied.

report.log - this is a text file that contains all error logger printouts from yaws.

Host.access - for each virtual host served by yaws, a file Host.access will be written which contains an access log in Common Log Format.

trace.http - this file contains the HTTP trace if that is enabled

auth.log - If configured, all http auth related messages goes here.

trace.traffic - this file contains the traffic trace if that is enabled

The default value for logdir is "."

ebin_dir = Directory

This directive adds Directory to the erlang search path. It is possible to have several of these command in the configuration file.

id = String

It is possible run multiple yaws servers on the same machine. We use the id of a yaws server to control it using the different ctl commands such as:

# /usr/local/bin/yaws -I foobar -s

To stop the Yaws server with id "foobar". Only the user that started the server called foobar is allowd to stop and control it. This is achieved through file permissions on the control file which will reside in "/tmp/yaws/foobar/ctl"

There can never be two yaws servers on the same machine with identical ids.

include_dir = Directory

This directive adds Directory to the path of directories where the erlang compiler seraches for include files. We need to use this if we want to include .hrl files in our yaws erlang code.

max_num_cached_files = Integer

Yaws will cache small files such as commonly accessed GIF images in RAM. This directive sets a maximum number on the number of cached files. The default value is 400.

max_num_cached_bytes = Integer

This directive controls the total amount of RAM which can maximally be used for cached RAM files. The default value is 1000000, 1 megabyte.

max_size_cached_file = Integer

This directive sets a maximum size on the files that are RAM cached by yaws. The default value i 8000, 8 kBytes.

cache_refresh_secs = Integer

The RAM cache is used to serve pages that sit in the cache. An entry sits in cache at most cache_refresh_secs number of seconds. The default is 30. This means that when the content is updated under the docroot, that change doesn't show until 30 seconds have passed. While developing a yaws site, it may be convenient to set this value to 0. If the debug flag (-d) is passed to the yaws start script, this value is automatically set to 0.

trace = traffic | http

This enables traffic or http tracing. Tracing is also possible to enable with a command line flag to yaws.

auth_log = true | false

Enable or disable the auth log. Default is true.

log_wrap_size = Integer

The logs written by yaws are all wrap logs, the default value at the size where they wrap around and the original gets renamed to File.old is 1000000, 1 M. This value can changed.

log_resolve_hostname = Bool

By default the client host IP is not resolved in the access logs.

fail_on_bind_err = Bool

Fail completely or not if yaws fails to bind a listen socket Default is true.

copy_error_log = true | false

Enable or disable copying of the error log. When we run in embedded mode, there may very well be some other systems process that is responsible for writing the errorlog to a file whereas when we run in normal standalone mode, we typically want the erlang errorlog written to a report.log file. Default value is true.

backwards_compat_parse = true | false

Versions of Yaws > than 1.41 changes the return value of the parse_query and parse_post functions. Earlier versions used {Key, Val} where Key was an atom. This made Yaws vulnerable for DOS attacks. Set this flag to keep the old deeprecated and vulnerable behaviour. I versions > that 1.41 the Key is a list/string.

username = Username

When running a Yaws server in production, it may feel safe to run yaws as a different user than root. Set this value to a non priviliged username on the system, such as "nobody". Yaws will initially have to run a root in order to properly listen to priviliged ports .

Yaws can virthost several webservers on the same ip address as well as several webservers on different ip addresses. The on limitation here is that there can be only one server with ssl enabled per each individual ip address. Each virttual host is defined within a matching pair of <server ServerName> and </server>. The ServerName will be the name of the webserver.

The following directives are allowed inside a server definition.

port = Port

This makes the server listen on Port

listen = IpAddress

This makes the server listen on IpAddress When virthosting several servers on the same ip/port address, if the browser doesn't send a Host: field, yaws will pick the first server specified in the config file. If the specified ip address is 0.0.0.0 yaws will listen on all local ip addresses on the specified port.

rhost = Host[:Port]

This forces all local redirects issued by the server to go to Host. This is useful when yaws listens to a port which is different from the port that the user connects to. For example, running yaws as a non-privileged user makes it impossible to listen to port 80, since that port can only be opened by a privileged user. Instead yaws listens to a high port number port, 8000, and iptables are used to redirect traffic to port 80 to port 8000 (most NAT:ing firewalls will also do this for you).

rscheme = http | https

This forces all local redirects issued by the server to use this method. This is useful when an SSL off-loader, or stunnel, is used in front of yaws.

access_log = true | false Setting this directive to false turns of traffic logging for this virtual server. The default value is true.

dir_listings = true | true_nozip | false

Setting this directive to false disallows the automatic dir listing feature of Yaws. A status code 403 Forbidden will be sent. Set to true_nozip to avoid the auto-generated all.zip entries.

docroot = Directory ...

This makes the server serve all its content from Directory.

It is possible to pass a space separated list of directories as docroot. If this is the case, the various directories will be searched in order for the requested file. This also works with the ssi and yssi constructs where the full list of directories will be searched for files to ssi/yssi include.

partial_post_size = Integer

When a yaws file receives large POSTs, the amount of data received in each chunk is determined by the this parameter. The deafult value is 10240.

tilde_expand = true|false

If this value is set to false yaws will never do tilde expansion. The default is false. tilde_expansion is the mechanism whereby a URL ob the form http://www.foo.com/~username is changed into a request where the docroot for that particular request is set to the directory ~username/public_html/ The default value is false.

allowed_scripts = [ListOfSuffixes]

The allowed script types for this server. Recognized are `yaws', `cgi', `php'. Default is allowed_scripts = yaws.

php_exe_path = Path

The name of (and possibly path to) the php executable used to interpret php scripts (if allowed). Default is php_exe_path = php.

appmods = [ListOfModuleNames]

If any the names in ListOfModuleNames appear as components in the path for a request, the path request parsing will terminate and that module will be called. There is also an alternate syntax for specifying the appmods if we don't want our internal erlang module names to be exposed in the URL paths. We can specify

appmods = <Path1, Module1> <Path2, Modules2> ...

Assume for example that we have the URL http://www.hyber.org/myapp/foo/bar/baz?user=joe while we have the module foo defined as an appmod, the function foo:out(Arg) will be invoked instead of searching the filesystems below the point foo.

The Arg argument will have the missing path part supplied in its appmoddata field.

errormod_404 = Module

It is possible to set a special module that handles 404 Not Found messages.

The function Module:out404(Arg, GC, SC) will be invoked. The arguments are

Arg is a #arg{} record

GC is a #gconf{} record (defined in yaws.hrl)

SC is a #sconf{} record (defined in yaws.hrl)

The function can and must do the same things that a normal out/1 does.

errormod_crash = Module

It is possible to set a special module that handles the HTML generation of server crash messages. The default is to display the entire formated crash message in the browser. This is good for debugging but not in production.

The function Module:crashmsg(Arg, SC, Str) will be called. The Str is the real crash message formated as a string.

arg_rewrite_mod = Module

It is possible to install a module that rewrites all the Arg #arg{} records at an early stage in the yaws server. This can be used to do various things such as checking a cookie, rewriting paths etc.

start_mod = Module

Defines a user provided callback module. At startup of the server, Module:start/1 will be called. The #sconf{} record (defined in yaws.hrl) will be used as the input argument. This makes it possible for a user application to syncronize the startup with the yaws server as well as getting hold of user specific configuration data, see the explanation for the <opaque> context.

revproxy = Prefix Url

Make yaws a reverse proxy. The Prefix is a path inside our own docroot and the Url argument is an url pointing to a website we want to "mount" under the path which is Prefix.

Example: revproxy = /tmp/foo http://yaws.hyber.org

Makes the hyber website appear under /tmp/foo

It is possible to have multiple reverse proxies inside the same server.

WARNING, this feature is yet not in production quality.

<ssl> .... </ssl>

This begins and ends an SSL configuration for this server.

keyfile = File

Specifies which file contains the private key for the certificate.

certfile = File

Specifies which file contains the certificate for the server.

cacertfile = File

File If the server is setup to require client certificates. This file needs to contain all the certificates of the acceptable signers for the client certs.

verify = 1 | 2 | 3

Specifies the level of verification the server does on clinet certs. 1 means nothing, 2 means the the server will ask the client for a cert but not fail if the client doesn't supply a client cert, 3 means that the server requires the client to supply a client cert.

depth = Int

Specifies the depth of certificate chains the server is prepared to follow when verifying client certs.

password = String

String If the private key is encrypted on disc, this password is the 3des key to decrypt it.

ciphers = String

* This string specifies the ssl cipher string. The syntax of the ssl cipher string is a little horrible sublanguage of its own. It is documented in the ssl man page for "ciphers".

</ssl>

Ends an SSL definition

<redirect> ... </redirect>

Defines an redirect mapping. The following items are allowed within a matching pair of <redirect> and </redirect> delimiters.

Path = [Scheme://]Host[:Port]

All accesses to Path will be redirected to [Scheme://]Host[:Port]Path. Scheme and Port is optional. The default is to use the servers scheme and port, rsheme and rport will be used if defined. To redirect all references to a site use "/" as Path.

<auth> ... </auth>

Defines an auth structure. The following items are allowed within a matching pair of <auth> and </auth> delimiters.

dir = Dir

Makes Dir to be controlled bu WWW-authenticate headers. In order for a user to have access to WWW-Authenticate controled directory, the user must supply a password. The Dir must be specified relative to the docroot.

realm = Realm

In the directory defined here, the WWW-Authenticate Realm is set to this value.

user = User:Password

Inside this directory, the user User has access if the user supplies the password Password in the popup dialogue presented by the browser. We can obviously have several of these value inside a single <auth> </auth> pair.

The usage of User:Password in the actual config file is deprecated as of release 1.51. It is prefered to have the users in a file called .yaws_auth in the actual directory. The .yaws_auth file has to be file parseable by file:consult/1

Each row of the file must contain terms on the form

{User, Password}.

Where both User and Password should be strings. The .yaws_auth file mechanism is not (yet) recursive. Thus any subdirectories to Dir are not automatically also protected.

The .yaws_auth file is never visible in a dir listing

</auth>

Ends an auth definition

<opaque> .... </opaque>

This begins and ends an opaque configuration context for this server, where 'Key = Value' directives can be specified. These directives are ignored by yaws (hence the name opaque), but can be accessed as a list of tuples {Key,Value} stored in the #sconf.opaque record entry. See also the description of the start_mod directive.

This mechanism can be used to pass data from a surrounding application into the individual .yaws pages.

keyfile = File

The following example defines a single server on port 80.

logdir = /var/log/yaws <server www.mydomain.org> port = 80 listen = 192.168.128.31 docroot = /var/yaws/www </server>

And this example shows a similar setup but two webservers on the same ip address

logdir = /var/log/yaws <server www.mydomain.org> port = 80 listen = 192.168.128.31 docroot = /var/yaws/www </server>

<server www.funky.org> port = 80 listen = 192.168.128.31 docroot = /var/yaws/www_funky_org </server>

An example with www-authenticate and no access logging at all.

logdir = /var/log/yaws <server www.mydomain.org> port = 80 listen = 192.168.128.31 docroot = /var/yaws/www access_log = false <auth> dir = secret/dir1 realm = foobar user = jonny:verysecretpwd user = benny:thequestion user = ronny:havinganamethatendswithy </auth>

</server>

An example specifying  a user defined module to be called
at startup, as well as some user specific configuration.
 
<server www.funky.org>
        port = 80
        listen = 192.168.128.31
        docroot = /var/yaws/www_funky_org
	start_mod = btt
	<opaque>
		mydbdir = /tmp
		mylogdir = /tmp/log
	</opaque>
</server>

And finally a sligthly more complex example with two servers on the same ip, and one ssl server on a different ip.

When there are more than one server on the same IP, and they have different names the server must be able to choose one of them if the client doesn't send a Host: header. yaws will choose the first one defined in the conf file.

logdir = /var/log/yaws max_num_cached_files = 8000 max_num_cached_bytes = 6000000

<server www.mydomain.org> port = 80 listen = 192.168.128.31 docroot = /var/yaws/www </server>

<server www.funky.org> port = 80 listen = 192.168.128.31 docroot = /var/yaws/www_funky_org </server>

<server www.funky.org> port = 443 listen = 192.168.128.32 docroot = /var/yaws/www_funky_org <ssl> keyfile = /etc/funky.key certfile = /etc/funky.cert password = gazonk </ssl> </server>

Written by Claes Wikstrom

yaws(1) erl(1)